It is a matter of common knowledge in the engineering of rolling bearings that deep groove ball bearings are rigid radial rolling bearings which cannot be disassembled, are distinguished especially by equally high radial and axial load bearing capacity and, owing to the low friction thereof, have the highest rotational speed limits of all bearings. These deep groove ball bearings consist essentially of an outer bearing race, an inner bearing race and a number of balls, disposed between the bearing races, as rolling elements which roll on groove-shaped ball raceways machined into the inside of the outer bearing race and into the outside of the inner bearing race and are guided at uniform distances from one another by a bearing cage. Radial ball bearings are filled with the balls by the eccentric assembly method disclosed by DE 168 499, in which the two bearing races are disposed eccentrically relative to one another and the crescent-shaped free space thereby formed between the bearing races is filled with the balls.
However, it has been found in practice that deep groove ball bearings of this kind have their limits in terms of the load bearing capacity of the bearing, owing to the small number of balls that can be installed as a maximum and the low maximum filling ratio of about 60%. In the past, therefore, a plurality of solutions were proposed, e.g. an unclosed filling opening disposed in the mutually opposite rims of the outer and the inner bearing race in accordance with DE 151 483 or a sealable filling opening of similar design in accordance with DE 24 07 477 A1, by means of which the intention was to achieve an increase in the filling ratio and hence in the load bearing capacity of deep groove ball bearings by increasing the number of balls. However, such filling openings have the disadvantage, both in the unclosed and in the closed embodiment, that the rolling elements may “stick” or jam at this filling opening, owing to the wedge-shaped entry of the latter into the ball raceways or owing to burrs, and therefore such solutions have not been accepted in practice.
Another possibility of increasing the number of rolling elements in a radial rolling bearing has furthermore been disclosed by DE 43 34 195 A1. In this radial rolling bearing, however, which is designed per se as a single-row deep groove ball bearing, the rolling elements are not formed by balls but by what are referred to as ball rollers, which are designed with two side faces that are flattened symmetrically as a departure from a basic ball shape and are disposed parallel to one another. Here, the width of these ball rollers between the side faces thereof is made less than the distance between the inside of the outer bearing race and the outside of the inner bearing race, thus allowing the bearing to be filled with the ball rollers by what is referred to as the axial assembly method, in which the ball rollers can be introduced into the bearing more or less horizontally and axially through the gap between the inner and the outer bearing race. When the center of the ball rollers is then at the level of the rolling element raceway axis, the ball disks are rotated by 90°, thus enabling them to roll in the rolling element raceways by means of their spherical bearing surfaces.
However, despite the possibility of inserting these specially designed ball rollers axially into the bearing, thereby enabling the radial rolling bearing to be filled with a large number of rolling elements, such a radial rolling bearing is at best only a compromise in respect of the intended increase in the load bearing capacity of the bearing. This is rooted in the fact that, because of their ability for axial introduction into the bearing, the ball rollers can be designed only with a correspondingly small width between the side faces thereof to enable them to be introduced into the bearing without problems through the gap between the inner and the outer bearing race. The rolling element raceways in the bearing races can likewise only be made relatively shallow and narrow in order to enable the rolling elements to be rotated into the operating position thereof without giving rise to an excessive radial play in the entire bearing in this operating position. However, the relatively narrow ball rollers and the shallow rolling element raceways lead to a relatively small contact area between the ball rollers and the rolling element raceways thereof, thus reducing both the axial and the radial load bearing capacity of such a radial bearing again and almost offsetting the original advantage of the increased number of rolling elements.
To avoid these disadvantages, DE 10 2005 014 556 A1 has therefore proposed to increase the width of the ball rollers between the side faces thereof to at least 70% of the diameter of the basic ball shape thereof and to design the groove-shaped raceways in the bearing races with a depth of about 19% and a width of about 75% of the diameter of the basic ball shape of the ball rollers since this gives a total contact area between the ball rollers and the raceways thereof of about 45% of the circumference of the basic ball shape of the ball rollers, which is also what the balls of conventional deep groove ball bearings have with respect to the raceways thereof in the bearing races. However, since the distance between the outside of the inner bearing race and the inside of the outer bearing race is thereby reduced to about 60% of the diameter of the basic ball shape of the ball rollers and is thus less than the width of the ball rollers, the insertion thereof into the radial rolling bearing was again achieved by the eccentric assembly method, in which the ball rollers are placed transversely in the raceways, in the free space between the two bearing races disposed eccentrically with respect to one another, with their side faces resting against one another, after which the inner bearing race is moved into the position concentric with the outer bearing race and, finally, the ball rollers are distributed at a uniform spacing on the pitch circle of their raceways and swiveled by 90°. The flattened side faces of the ball rollers made it possible here for an increased number of rolling elements to be introduced into the ball roller bearing as compared with single-row deep groove ball bearings, giving a filling ratio of about 73%, even with the eccentric assembly method.
Although it has been possible to ensure with a ball roller bearing designed in this way that the ball rollers have large contact areas with respect to their raceways in the bearing races, like the balls of a deep groove ball bearing, and that the ball roller bearing can be fitted with a larger number of rolling elements and with a higher filling ratio than conventional single-row deep groove ball bearings, it was necessary, owing to the eccentric assembly method, to make compromises in terms of the number of rolling elements compared with the higher number of rolling elements possible in the axial assembly method. Thus, although it was possible to reduce the axial installation space and the weight of the ball roller bearing and increase the axial loading capacity thereof in comparison with conventional deep groove ball bearings, the increase in the radial load bearing capacity of the ball roller bearing was however comparatively small.